Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$53.71	10.200%	$59.1884	$59.19	$59.20	$59.20
Purchase #2	$6.98	13.492%	$7.9217	$7.92	$7.90	$7.90
Purchase #3	$162.91	6.704%	$173.8315	$173.83	$173.85	$173.80
Purchase #4	$61.37	7.122%	$65.7408	$65.74	$65.75	$65.70
Purchase #5	$136.99	7.502%	$147.267	$147.27	$147.25	$147.30
Purchase #6	$12.59	12.793%	$14.2006	$14.20	$14.20	$14.20
Purchase #7	$101.60	4.244%	$105.9119	$105.91	$105.90	$105.90
7 purchase totals =	$536.15		$574.0619	$574.06	$574.05	$574.00